STRUCTURAL STUDIES AND THEIR BEARING ON THE EARLY PRECAMBRIAN HISTORYOF THE DHARWAR TECTONIC PROVINCE, SOUTHERN INDIA

In the Dharwar tectonic province, the Peninsular Gneiss was considered to mark an event separating the deposition of the older supracrustal Sargur Group and the younger supracrustal Dharwar Supergroup. Compelli ng evidence for the evolution of the Peninsular Gneiss, a polyphase mi gmatite. spanning over almost a billion years from 3500 Ma to 2500 Ma negates a stratigraphic status for this complex, so that the decisive argument for separating the older and younger supracrustal groups lose s its basis. Correlatable sequence of superposed folding in all the su pracrustal rocks, the Peninsular Gneiss and the banded granulites, ind icate that the gneiss 'basement' deformed in a ductile manner along wi th the cover rocks. An angular unconformity between the Sargur Group a nd the Dharwar Supergroup, suggested from some areas in recent years, has been shown to be untenable on the basis of detailed studies, A num ber of small enclaves distributed throughout the gneissic terrane, wit h an earlier deformational, metamorphic and migmatitic history, provid e the only clue to the oldest component which has now been extensively reworked.